Module 5 - Photosynthesis

Question 1

What is photophosphorylation?

Answer 1

This is when u add a phosphate molecule using light

Question 2

What is Photolysis?

Answer 2

The splitting up of a molecule using light energy

Question 3

What is photoionisation?

Answer 3

When light energy provides energy to an electron which excites them and therefor causes them to be released.

Question 4

What is Decarboxylation?

Answer 4

The removal of carbon dioxide from a molecule

Question 5

What is Dehydrogenation?

Answer 5

The removal of hydrogen from a molecule

Question 6

What are 3 types of photosynthetic pigment that chlorophyll?

Answer 6

Chlorophyll a, chlorophyll b and carotene.

Question 7

Where are photosynthetic pigments within a chlorophyll found and what is the name of the product they are bound to called?

Answer 7

They are found in thylakoid membranes and a attached to a protein which produces a product known as the photosystem.

Question 8

What are both photosystems called and what are their wavelengths at which they absorb light from?

Answer 8

Photosystem I - wavelength of 700nm
Photosystem II - wavelength of 680nm

Question 9

What are the two types of reactions that photosynthesis is split into?

Answer 9

The light-dependent reaction and the light-independent reaction

Question 10

In the light-dependant reaction, what happens when the light is absorbed by the chlorophyll?

Answer 10

When the chlorophyll absorbs the light energy, this excites the electrons and then causing them to be released - they become photoionized. Some of the energy from the release of electrons is used to make ATP from ADP and some is used to make reduce NADP from NADP. 02 is oxidised

Question 11

What is the difference between where both reactions take place?

Answer 11

The light dependent reaction takes place in the thylakoid membrane and the light independent reaction takes place in the stroma.

Question 12

How are products from the light dependent reaction used to produce products in the light independent reaction?

Answer 12

The ATP and Reduced NADP from the light dependent reaction supply the energy and hydrogen to make simple sugars from CO2

Question 13

What are the names of both types of photophosphorylation?

Answer 13

Cyclic and non-cyclic

Question 14

How are photosystems connected and what do they carry?

Answer 14

Photosystems are linked via electron carriers that create an electron transport chain that allows excited electrons to flow through. A chain of proteins.

Question 15

Explain the first stage of Non-Cyclic photophosphorylation - the exciting of electron

Answer 15

In PS11, the light energy is absorbed which excites the electrons causing them to move to a higher energy level and so move down the electron transport chain to PS1.

Question 16

Explain the second stage of Non-cyclic photophosphorylation - photolysis

Answer 16

The moving of electrons down to PS1 means electrons in PSII must be replaced. This then means light splits water molecules into protons H+ ions, electrons and water

Question 17

Explain the third stage of Non-cyclic photophosphorylation - making ATP

Answer 17

When electrons move down the electron transport chain, they lose energy which provides energy for protons to be transported into the thylakoid membrane so that the membrane has a high conc than the stroma. Then, protons move down the concentration gradient via ATP synthase which also provides energy for ADP and Pi to form ATP

Question 18

Explain the forth stage of non cyclic photophosphorylation - and generates reduces NADP

Answer 18

Light energy is then absorbed by PS1 which excites the electron to an even high level. The electrons can be transferred to NADP along with a proton from the stroma to form reduced NADP

Question 19

What exactly is the chemiosmotic theory?

Answer 19

The process of electrons moving down the electron transport chain creating a proton gradient to drive ATP synthesis is known as chemiosmosis.

Question 20

Where does the calvin cycle take place and what does it produce?

Answer 20

Takes place in the stroma and ribulose bisphosphate and triose phosphate

Question 21

Describe the first stage of the calvin cycle - production of glycerate 3-phosphate

Answer 21

This is when co2 enters the stomata and binds to ribulose bisphosphate, catalysed by the enzyme rubisco. Because ribulose bisphosphate is a 5-carbon compound, when they bind they produce a unstable 6 carbon that quickly breaks down into glycerate 3-phosphate

Question 22

Describe the second stage of the calvin cycle - reduction of GP to triose phosphate

Answer 22

This is where hydrolysed ATP and reduced NADP are used to reduce GP. The hydrolysed ATP provides energy and the reduced NADP provides H+ ions. The product either produces organic compounds or remains in the cycle to remake ribulose bisphosphate

Question 23

Describe the third stage of the calvin cycle - the regeneration of ribulose bisphosphate

Answer 23

5 out of 6 are used to regenerate ribulose bisphosphate and the rest of the energy produced from hydrolysed ATP is used to regenerate it.

Question 24

How are organic substances produced using GP and TP?

Answer 24

Carbohydrates - 2 triose phosphate molecules
Lipids - Glycerol (synthesis from triose phosphate) anf fatty acids (synthesised from glycerate 3-phosphate)

Question 25

Why does the calvin cycle need to turn 6 times to produce one hexose sugar?

Answer 25

5 of 6 TP produced are used to regenerate ribulose bisphosphate. This means every 3 turns, 6 TP are produced but 5 are not used which leaves one TP. But 2 TP’s are needed to make one hexose sugar which means the cycle has to turn another 3 times - in total 6 times - to produce 2 TP and one hexose sugar.